Fall Ideal Time for Soil Sampling

Fall is the ideal time of year to conduct routine soil sampling of your lawns, gardens, and cropland. Not only are weather conditions typically more favorable as compared to the spring season, but you will then have the winter months to think about upcoming management decisions based on the soil analysis. Here are some other reasons why fall is better than spring, or any other season, for soil sampling:

1. Fall Provides Ideal Conditions for Accurate Sampling – Most soil sample reports are inaccurate. They are not representative of the area being sampled, primarily because not enough cores were taken. University of  Missouri Extension recommends a minimum of 15 to 20 cores from the area being sampled. An adequate number of cores is usually not collected in the summer because the ground is hard and it’s hot outside. An  adequate number of cores may not be collected in the spring because the ground may be overly wet and collecting a quality core may be difficult.  Fall provides pleasant working conditions as well as soil that is not too dry or wet. 

2. Lime Can Be Applied in a Timely Manner – On most ground in Missouri, occasional liming is necessary to maintain an adequate pH for crops. After lime is applied it can take up to 6 months for the lime to raise the pH of the soil to the required level. Applying lime in the fall will ensure that the pH is correct in time for a  spring-planted crop. 

3. Fertilizer Can Be Purchased Prior to the End of the Year – Fertilizer is often cheaper in the fall or the winter than it is in the spring when demand is greatest. If you sample in the fall, you will know exactly what you need and you can purchase it when prices are lowest. Purchasing fertilizer needed for next year prior to the end of this year could potentially provide some tax advantages. Check with your tax professional. 

4. Soil Testing Laboratories Aren’t as Busy in the Fall – The majority of farmers, gardeners, and homeowners test their soil in the spring.  Soil testing labs are swamped this time of year and it can take several weeks to get results.  This is often too late to timely apply fertilizer. Turnaround time in the fall is much faster. 

5. Fall is Ideal Time for Phosphorus and Potassium or Manure Applications – Phosphorus and potassium applied in the form of commercial fertilizer and nearly all nutrients applied in manure form are not immediately  available to the plant.  It takes time for these nutrients to become available for a plant to use.  So if you apply these products in the spring, they may not necessarily be available for that year’s crop.  If you apply in the fall, they will be of benefit to the next year’s crop. And, to know how much to apply, you need a soil test. 

Even if you begin sampling in the ideal fall time-frame, or even if you already do, the results are only as good as your sampling methods.  University of Missouri Extension has a number of guides on properly sampling pastures, lawns, or crop fields available on their website, extension.missouri.edu, or at your county extension office. 

Source: Travis Harper, Agronomy Specialist